'Air fuelled' battery tech invented in Scotland

Oxygen-sucking kit won't be popular in submarines

Boffins based in Scotland believe they're on the track of rechargeable batteries which could broach a barrel of whup-ass on any now in service - and even more advanced types in development. The new super batteries gain their advantage by absorbing atmospheric oxygen as they discharge, and giving it up again as they charge.

News of the developments comes from the Engineering and Physical Sciences Research Council, one of Blighty's main tech funding bodies. The EPSRC are chuffed as ninepence with the so-called STAIR battery - short for St Andrews Air - under development at the Scottish uni by Professor Peter Bruce and his team.

"Our target is to get a five to ten fold increase in storage capacity, which is beyond the horizon of current lithium batteries," says Bruce. "The key is to use oxygen in the air as a re-agent, rather than carry the necessary chemicals around inside the battery."

Bruce and his team give some details of the STAIR technology here, under the less snappy tag "lithium oxygen battery". As the battery discharges, lithium ions from the electrolyte combine with electrons from the circuit and oxygen from the air around to produce lithium Li2O2. As the battery is charged up again, restocking it with lithium ions, the oxygen is emitted once again.

Bruce and his crew say that they "have demonstrated evolution of O2 on charging". They also say that "values of 1220 mAhg-1 are, in principle, possible". The accompanying diagram seems to indicate that this refers to a discharge voltage in the region of 2.5V or so.

As Wolfram Alpha tells us, that equates to a potential specific energy density of 3050 Wh/kg (around 19 times normal li-ion battery performance), handily trumping even the possibly-snazzy new lithium-sulphur tech which BASF have just jumped into. The scope is plainly there to achieve the five to tenfold storage boost that Professor Bruce is aiming at.

The prof reckons his kit, in addition to being light, could be cheap, as the porous carbon matrix which holds the Li2O2 ought to be economical. Nonetheless he cautions that his kit won't be ready for prime time for five years at least.

If STAIR ever goes mainstream, users may need to be a little careful about battery charging (at least in large applications like electric vehicles). A build-up of oxygen in a confined space is a significant fire and explosion risk.

On the other side of the coin, you wouldn't want to use STAIR batteries in some applications - for instance, propelling submarines underwater - as they'd tend to suck all the oxygen out of the hull atmosphere, with fatal results for any humans therein. ®